The proposed research will use large unilamellar liposomes as models of biological cells. The relationship between the osmotic response of a given liposome and its membrane chemical composition and temperature will be determined experimentally. Equilibrium and non-equilibrium cases will be considered and the data interpreted in terms of standard thermodynamic analyses. The results will provide important biophysical data related to the mechanisms of membrane transport for liposomes aand the more complex biological cell. Computer simulations of liposome water and permeable solute transport during freezing will be compared to experimental results using our cryomicroscope system. Fluorescent techniques will be used the cryomicroscope to define the nature of membrane freezing injury. Quantitative fluorescent and phase contrast microscope photometry will be applied to distinguish between unilamellar and multilamellar liposomes. A new microscope observation chamber will be developed to directly observe liposome osmotic response. this technique of direct access to osmotic volume change in a well-defined single bilayer structure represents an improvement with respect to most previous liposome osmotic research. The proposed research is part of a long-term program aimed at developing thermo-dynamic models for predicting membrane response (including damage) produced by a variety of external disturbances. such models would have predictive and therapeutic value in such health-related areas as cryopreservation, cryosurgery, hyperthermia, and burn injury.